Wave guide attenuator



Oct. 9, 1951 FIG.

W. A. JOERNDT ET AL WAVE GUIDE ATTENUATOR 3 Sheets-Sheet l 26 7 I l. I] 35 1- 46 lg 29 47 5 EL 54 r L 45- 53a 2 52b 57 52c FIG. 2

INVENTORS. WILBUR A. JOERNOT ROLAND W. LARSON ATTORNEY 1951 w. A. JOERNDT ET AL ,570,813

WAVE GUIDE ATTENUATOR Filed Oct. 8, 1948 3 Sheets- Sheet 2 FIG. 5

INVENTORS. WILBUR A. JOERNDT ROLAND W. LARSON ATTOR N EY Filed 0013- 8, 1948 1951 w. A. JOERNDT ET AL 2,570,813

WAVE GUIDE ATTENUATOR I 3 Shee ts-Sheet 3 INVENTORS. WILBUR A. JOERNDT ATTORNEY Patented Oct. 9, 1951 WAVE GUIDE ATTENUATOR Wilbur A. J oerndt, Silver Spring, Md., and Roland W. Larson, Marshfield, Wis., assignors to the United States of America as represented by the Secretary of the Navy Application October 8, 1948, Serial N 0. 53,542

The present invention relates generally to radio direction and ranging (radar) and more particularly to an attenuator for a radar receiving antenna. Still more specifically, the invention relates to an automatically variable attenuator for use in connection with a radar receiver mounted in a guided missile or other projectile for maintaining a substantially constant power input to the receiver as the missile moves with respect to a signal source.

In certain guided missiles, control is effected by radar. Broadly stated, such control involves the use of radio-receiving apparatus in the missile, as well as transmitting equipment located remotely therefrom, said receiving apparatus ineluding a detector, an amplifier and various electro-mechanical translating devices. The receiver detector usually comprises a crystal rectifier which is mounted in a wave guide section andis positioned near the receiving antenna which, in some arrangements, is constituted by ahorn. The entire assembly is mounted in'the' missile, with the horn directed rearwardly. For best results, control of the missile must be effectuated as soon as possible after it is launched. Such control introduces a difficulty'in that the power necessary for control at a distance is too great at the launching location, with the result thatthe-detector crystal may be ruined. Accordingly,

it'is necessary to attenuate the received signal atthe start approximately in proportion to itsstrength in order to prevent overloading of the crystal. -Moreover, since the received power varies inversely as the square of the distance from the transmitter, said attenuation must be varied in a like manner.

One of the principal objects of the present invention, therefore, is to provide an attenuator for the purpose set forth which will operate to prevent-ruination of radar receiver detector crystals by strong radio control signals.

It is another object of the invention to provide means for attenuating a signal received by a guided missile in such a manner that said missile V guiding means will receive a signal of optimum strength throughout its flight.

A further object of the invention is to provide a simple and highly eflicient attenuator which embodies but few working parts, is readily adaptwill, therefore, function" to attenuate a received 3 Claims. (01. 17844) signal immediately upon launching of a missile. And a further object of the invention resides in the provision, in an attenuator for the purpose set forth, of simple and highly efficient releasing means. Other objects and many of the attendant advantages of this invention will be readily appreciated as the same becomes understood by reference to the following detailed description when considered in connection with the accompanying drawings, wherein:

Fig. 1 is a side elevation of the invention installed on a guided missile and mounted'in a wave guide between the antenna horn and the crystal detector, the attenuator element "femployed being shown in unreleased, full attenuating, position; i Fig. 2 is an enlarged elevation, at right angles to that shown in Fig. 1, partly in section, on the line 2-2 of Figure 1;

Fig. 3 is an enlarged side elevation, partly in section, showing the device with the attenuator element and associated mechanism in minimum attenuating position;

Fig. 4 is an enlarged side elevation similar to Fig. 3; but showing the attenuator mechanism in maximum attenuating position;

Fig. 5 is a vertical sectional view, still further enlarged, on the line 55.of Fig. 4; and

Fig. 6 is an enlarged detail sectional view of the dashpot forming a part of the release mechanism. Stated briefly, the present invention attains the objects enumerated hereinabove by providing simple means constituted principally by a straight blade pivoted to swing, through a longitudinally arranged slot in a wave guide section, into and out of the guide from a full attenuating to a full'non-attenuating position, a spring-operated, dashpot-damped blade shifting mechanismguand adjustable, inertia operated mechanism foiflJreleasing the blade shifting mechanism when the missile on which the attenuator is mountedis launched. The shifting mechanism is adjustable in such a manner that the time required" for movement of the'blade from attenuating to mnattenuating positions may be predetermined to suit the particular conditions under whichmissile control is to be elfectuated. Referring now to the drawings in detail, a wave guide section, which constitutes the body or frame of the invention, is shown at In. The section II] is provided with a base member .llla, and at'corresponding ends of said section' and base member are connecting flanges II and I2.

.5 A receiving horn |3, of conventional generally frusto-pyramidal design, is connected to the section H] by a wave guide section l4, which is provided with a flange l bolted to the flange l2. Similarly, a crystal detector l6, mounted on a wave guide section I1, is connected to the opposite end of thesection H1. The section I! is provided with a flange l8 which is bolted to the flange As best seen in Figures 3, 4 and 5 of the drawings, the top wall of the wave guide section In is formed, medially of its width, with a longitudinally extending slot 20, the purpose for which will be pointed out in detail hereinafter.

A yoke 2|, of generally 2 shape, is mounted on the section II) and flange II, and pivotally mounted between the lower. arms of said yoke, by a pin 22, is an attenuator having a clamp or stiffening channel-member 23 which carries an attenuator blade or element 24. The element 24 may be swung into and out of the slot to attenuate the signal passing through the guide. As best seen in Fig. 3, the lower corner of the end of the element nearest the yoke 2| is beveled, or cut away so that no part of said element extends into the slotwhen the attenuator is fully retracted. ';I;he 'mechanism for swinging the clamp and attenuator element to raised, non-attenuating position includes a dashpot 25, the construction of which is best shown in Figure-6. By referring to this view it will be seen that the. dashpot includes a cylinder 26 inwhich is mounted a piston 27 haying a preferably leather Washer 28. The piston 21 and washer 28 are secured to a plunger 29byabolt30.v

The end wall 3| of the dashpot cylinder 26 is formed with a port 32 which registers with an intake port 33 of a valve 34 carried in a mounting block 35 suitably secured to the outer surface of said wall 3|. The valve 34 includes a cylindrical chamber 350. reduced near one end to define a valve seat 36 and a discharge port 31. A stem 38 isformed with a rounded inner end, for cooperation with the valve seat 3-6, and with an enlarged threaded rear portion 39 mating with a threaded course in the block 35. The outer end of the portion 39,; is slotted to receive a screw driver bit and a lock nut 40. is provided for securing the stem 38against accidental displacement; v

The plunger is provided, near its free end, with a transverse pin 4|. As will be seen, the pin 4| extends at each side ofthe plunger 29, for a reason to be explained in detail hereinafter. The plunger 29 extends through a head 42 which closes the cylinder .at itsforward end. The head 42 is extended and recessed to define a cup 43, and surrounding the plunger is a coil spring 44 having one end engageable with the face of thepiston 21 and its opposite end engageable with the end wall of the cup, a substantial portion of the spring being positioned in thecup. As will be obvious, the spring 44 urges the piston toward the rear wall 3| of the cylinder.

qBy referring again to Figures 1 to 5 of the drawings, it will be seen that the block is pivotally mounted between the arms of the yoke 2 near their free ends, by a pin 45. v

The plunger 29 is pivotally connected to the clamp 23 by a link 46, best seen in Figures 2 and 5,- saidlink having one end straddling the free end' of the plungerand pivotally mounted thereon .by pin4| and its other end pivotally'mounted between a pair of plates 41 on the clamp 23 by a: pin 48. A sleeve 480. spaces the arms of the 4 link apart. The link connection between the plunger and the clamp is necessary to afford a limited amount of play, to prevent freezing of said plunger.

A retractile spring 49 is tensioned between the forward end of the cylinder of the dashpot 25, therebeneath, asshownin Fig. 1, and a pin 50 carried by the midsection of the yoke 2|, and serves to retain said cylinder and the attenuator under tension.

The attenuator element 24 is initially held in full attenuating position by release mechanism now to be described. The release mechanism is shown generally at 5| and includes a generally E-shaped frame or bracket 52 the long shank of which is secured to one side wall of the section ID by screws 53. As best seen in Figs. 2 and 5, an arm 52a of the bracket is shaped to define a yoke 53a having spaced arms, pivotally mounted between which is one end of a latch member 54. The latch member includes a hub 54a and a finger 55 which is connected to the hub by a-web defining a crotch 56, the walls of which are inclined. As best seen in Figures 1' and 2 of the drawings, the finger 55 when in latching position liesin generally parallel spaced relation to the long shank of the bracket 52. The finger 55 isthickened at its free end and formed with a socket, for" a purpose soon to become evident. The bracket 52 includesan intermediate. arm 52b and an end arm 520 which are apertured near their free ends freely to receive a latch pin 57, one end of which is removably engageable in the socket in the end of. the finger 55. .7 A weight 58, of suitable mass, is secured to the pin 51 be tween the intermediate arm and the arm- 52c and is sodesigned that it will be movable between said arms for shifting an end of said pin 5'| into orout of engagement with the finger 55.

The operation of the invention will scribed. r g 7 I The device is first adjusted, .within'or on the guided missile, to place the attenuator with the. element 24 in full attenuating position. That is, the element-24 is fully extended into the slot 20. In this position the plunger 29 is fully projected and the spring 44 (Figure 6) is fully compressed.- The plunger and element are maintained in the; position above described by the engagement of the now be definger 55 with one end of the pin 4|, said-pin be:

ing disposed againstthe outermost inclined wall of the crotch 55, the confronting end of the pin 51 being in the socket in the thickened free endof said finger.

When the missile is launched, the-weight '58 and the pin 51 secured thereto will slide; by inertial.

forces, toward the end arm 520, for withdrawing the end of the pin 51 from the socket in the end of the latch finger 55 and releasing said latch: The latch flies over, by the action of the spring 44, to release the transverse pin 4|. Upon release of said pin 4|, the spring 44 forces the piston 21 away from the head of the dashpot, applying;

pressure to fluid in the dashpot and drawing in the plunger 29. plunger produces partial rotation of the link 46 about the pin 48. This motion is provided to tating about the pin 48, further motion .of the plunger 29 produces angular movement ofthe. attenuator cylinder about the pin 45, removing the,

element from the slot in the wave guide and re The initial movement of the,

ducing attenuation of energy passing therethrough. The rate of this removal is controlled by the adjustable valve in the block 35, which regulates the escape of air from the cylinder and hence the speed of the plunger 29. The valve is adjusted to produce a removal rate which will completely remove the attenuator element when the missile reaches a position where the received signal energy can not damage the crystal.

Obviously many modifications and variations of the present invention are possible in the light of the above teachings. It is therefore to be understood that within the scope of the appended claims the invention may be practiced otherwise than as specifically described.

We claim:

1. In an attenuator for use with an ultra high frequency radio receiver having a crystal detector, a receiving antenna, a wave guide connecting said antenna to said detector to convey the received signals to said crystal, said wave guide having a slot passing through its wall and extending substantially longitudinally of the guide, a sheet of electrically conductive material, means supporting said sheet for pivotal motion through the slot, resilient means tending to withdraw the said sheet from the wave guide, a latch initially holding the sheet fully projected into the wave guide, and means actuable by inertia to release said latch.

2. In an attenuator for use with an ultra high frequency radio receiver having a crystal detector, a receiving antenna, a wave guide connecting said antenna to said detector to convey the received signals to said crystal, said wave guide having a slot passing through its wall and extending substantially longitudinally of the guide, a sheet of electrically conductive material, stifiening means supporting said sheet for pivotal motion through the slot, resilient means tending to withdraw the said sheet from the wave guide, a dashpot device opposing motion of said sheet, a latch initially holding the sheet fully projected into the wave guide, and means actuable by inertia to release said latch, whereupon the resilient means withdraws the sheet from the wave guide at a rate modified by the dashpot.

3. In an attenuator for use with an ultra high frequency radio receiver having a crystal detector, a receiving antenna, a wave guide connecting said antenna to said detector to convey the received signals to said crystal, said Wave guide having a slot passing through its wall and extending substantially longitudinally of the guide, a sheet of electrically conductive material, a stiffening member extending along one edge of the sheet and supporting said sheet for pivotal motion through the slot, a spring tending to withdraw the said sheet from the Wave guide, a latch initially holding the sheet fully projected into the wave guide, adjustable retarding means resisting the motion of said sheet and means actuable by inertia to release said latch, whereupon the spring withdraws the sheet from the wave guide at a rate controlled by the strength of the spring and the resistance of the adjustable retarding means.

WILBUR A. J OERNDT. ROLAND W. LARSON.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Name Date Hollingsworth et al. Feb. 8, 1949 OTHER REFERENCES Number Practical Analysis of Ultra High Frequency, by 

